Method for preparing vapor-phase isomerization catalyst



Unite States 3,020,2ii Patented F ab. 6, 1962 ice 3,020,241 METHOD FORPREPARING VAPOR-PHASE ISOMERIZATIGN CATALYST John A. Ridgway, Jr., andBuell OConnor, Texas City, Tex., assignors, by mesne assignments, toStandard 011 Company, Chicago, 111., a corporation of Indiana NoDrawing. Filed Nov. 17, 1958, Ser. No. 774,085

8 Claims. (Cl. 252-439) The present invention relates to a method forpreparing a vapor-phase isomerization catalyst and, more particularly,to a method for treating a chlorine-containing, platinum-aluminareforming catalyst so as to make it highly selective and effective forthe vapor-phase isomerization of parafilns.

With the persistent rise in the octane number of motor fuels, petroleumrefiners have rapidly expanded catalytic reforming with platinumcatalyst to the point where available reforming feedstocks are beingexhausted. As a result, refiners are now turning to other processes fortane improvement, a particularly attractive process being isomerization.In the isomerization process, light paraflins, such as normal pentaneand normal hexane, are converted to isomers, having substantially higheroctane numbers, e.g., isopentane, 2,2-dimethylbutane (neohexane),2,3-dimethylbutane (diisopropyl), and the like.

Various isomerization processes and catalysts are available, but all ofthem suffer from one or more shortcomings such as highly-corrosivecatalyst systems, relativelylow catalyst activity, catalyst regenerationdifficulties, costly method of catalyst preparation, and the like. Wehave now discovered a method for preparing a highlyactive isomerizationcatalyst which results in a process which is relatively free of suchdifficulties. Our advantageous method of catalyst preparation has theadditional attribute of being able to convert a highly-active reformingcatalyst to a catalyst which is highly selective and effective forparaflin isomerization. Thus the same catalyst plant can turn out bothreforming catalyst and simultaneously, with the addition of a fewpreparation steps, a highly-active isomerizatio-n catalyst. These andother advantages of our invention will become apparent as the detaileddescription proceeds.

In accordance with the present invention a. vapor-phase isomerizationcatalyst is prepared bythe method which comprises impregnating solid,hydrous alumina containing between about 1 to 30 percent by weight ofcombined water in the presence of between about 0.001 to 0.02 mole ofaluminum chloride per mole of dry A1 0 with a solution of a platinumcompound whereby platinum is added thereto in a proportion between about0.01 and 2.0 percent by weight, based on dry A1 0 drying and calcining,impregnating the resulting composite with hydrogen fluoride to afluoride level in the range of about 0.5 to 5 percent by weight, basedon dry A1 0 exposing the composite to a substance selected from thegroup consisting of sulfur, sulfur-containing compounds, and mixturesthereof in SllifiCiGIlt quantity so that the catalyst is contacted Withat least about 0.1 percent by weight of sulfur, based on dry A1 0 andthereafter again calcining.

ously with aluminum chloride as an aqueous solution of chloroplatinicacid and aluminum chloride, or it may be added before or after thesolid, hydrous alumina is contacted with aluminum chloride, preferablyaqueous aluminum chloride. fluoride, the platinum-containing compositeis dried, e.g., at 150 to 400 F. for 0.5 to 24 hours, and calcined,e.g., at 400 to 1200" F. for 0.5 to 24 hours. Hydrogen fluoride is thenadded, usually as aqueous hydrogen fluoride, in sufficient quantity sothat the fluorine level of the resulting composite is in the range ofabout 0.5 to 5 percent by weight, based on dry A1 0 Thehydrogen-fluorideimpregnated composite is then exposed, before or afteragain being calcined, to contact with at least about 0.1 percent byWeight of sulfur, e.g., about 0.1 to 5 percent by weight ofsulfur. Theexposure to sulfur may be in the vapor-phase or liquid-phase, preferablyin the liquidphase. In either case the contacted composite should thenbe calcined before being employed for isomerization.

When contacting the composite with sulfur in the liquid-phase, We preferto use aqueous solutions of sulfur compounds, e.g., aqueous solutions ofhydrogen sulfide, ammonium sulfide, and ammonium polysulfide. Whencontacting the composite with sulfur in the vapor-phase we may also use,in addition to hydrogen sulfide, ammonium sulfide, and ammoniumpolysulfide, other sulfur compounds such as mercaptans, carbondisulfide, and the like. As above mentioned, the catalyst should berecalcined prior to employing it for isomerization regardless of themethod of sulfur treatment. For best results, we have found that theliquid-phase treatment, followed by recaicination, is much preferred.While the sulfur treating step exposes the catalyst to substantialsulfur levels, it should be understood that the subsequent calcina-tionremoves a substantial portion of the sulfur. The finished cggalyst maythus contain only a fraction of the sulfur so a ed.

In accordance with the best mode contemplated, the present invention iscarried out by first preparing a platihum-alumina composite, orobtaining a platinum-alumina composite already prepared, by impregnatingsolid, hydrous alumina containing 1 to 30 percent by weight of combinedwater in the presence of between about 0.001 to 0.02 mole of aqueousaluminum chloride per mole of dry A1 0 with an aqueous solution ofchloroplatinic acid whereby the platinum is added thereto in aproportion 7 between 0.01 and 2 percent by weight, based on dry Prior tothe above-described step of impregnating the platinic acid. The platinummay be added simultane- AI O After drying and calcining, the compositeis impregnated with aqueous hydrogen fluoride to a fluoride level ofabout 1.5 percent by weight, based on dry A1 0 We again dry and calcineand thereafter expose the composite to an aqueous solution of ammoniumsulfide in suificient quantity so that the catalyst is contacted withabout 0.9 percent by weight of sulfur, based on dry A1 0 following whichthe catalyst is again dried and calcined.

The resulting composite has been found to be highly selective forisomerization of paraflins, particularly the isomerization of C to Cparaflinic hydrocarbons. Effective conditions for isomerization of suchhydrocarbons with our catalyst includes aternperature in the range ofabout 500 to 800 F., preferably 550 to 750 F.; apressure of atmosphericor higher, e.g., atmospheric to 500 p.s.i., preferably 50 to 250 psi; 21space velocity of about 0.1 to 10, preferably 0.5 to 5.0, optimally 1,5to 3.0; and a hydrogen rate of about to 10,000 standard cubic feet perbarrel of hydrocarbon charge, preferably 500 to 5,000. The catalyst hasthe additional advantage of being readily regenerated by a simple carbonburnoif, e.g., by contacting with oxygen-containing gas at temperaturesabove about 600 F. 1

Prior to impregnating with hydrogen Example I A platinum-aluminacomposite was prepared by gelling, drying and calcining a Heard-typealumina hydrosol (Heard Reissue No. 22,196, October 6, 1942), to avolatiles content of about 1 to percent by weight, based on dry A1 0 andthereafter impregnating the calcined alumina with an aqueous solution ofchloroplatinic acid and aluminum chloride in sufficient quantities sothat, after again drying and calcining, the resulting compositecontained about 0.6 percent platinum and about 1.1 percent of chlorine.The resulting composite was found to be highly effective for thecatalytic hydroforming, under well-known reforming conditions, offull-boiling-range naphthas, having CFRR clear Octane numbers in therange of about 35 to 70, to octane levels in excess of about 100.

The resulting composite was thereafter tested, both before and aftertreatment in accordance with the present invention, to determine itsisomerization activity. In one experiment the composite was testedwithout any contact with hydrogen fluoride or sulfur. In a secondexperimenL'the composite was tested after being treated with aqueoushydrogen fluoride to a fluoride level of about 1.5 percent by weight,based on dry A1 0 following which it was dried and calcined. In a thirdexperiment the composite was tested after being contacted with anaqueous solution containing about 0.9 percent by weight, based on dry A10 of sulfur in the form of ammonium sulfide, following which it wasdried and calcined. In the fourth experiment, which illustrates thepresent invention, the composite was tested after being treated with anaqueous hydrogen fluoride solution to a fluoride level of about 1.5percent by weight, based on dry A1 0 following which it was dried andcalcined and contacted with an aqueous solution containing 0.9 percentby weight, based on dry AliO of sulfur in the form of ammonium sulfideand again dried and calcined.

Each of the above catalysts were tested under isomerization conditionsincluding the particular temperatures which resulted in the maximumproduction of neohexane for that particular catalyst. Neohexane yieldwas used as one measure of activity since such component has a veryhighoctane number and is a highly-desirable product from an isomerizationprocess. At the same time, it is also highly desirable to minimize thecracking reactions so that charge stock, which is not isomerized, is notconverted to'gas, and thus unavailable for gasoline blending and/orpossible recycle operatiou' Thus, rnaximum'neohexane and minimum crackedproduct are both measures of a superior catalyst.

" The iso'meriza-tion activity tests were carried out utilizing acombined microreactor-gas chromatography assembly similar to unitsdescribed by Emmett (Paul H. Emmett, Advances in Catalysis, vol. IX, p.645-648, 1957, Academic Press, Inc., Publishers, New York, N.Y.), and byMarchal et al. (I. Marchal, L. Convent, I. van. Rysselberge, Revue delInstitut Francais du Ptrole 12, 1067-1074, 1957). The reactor andchromatograph column were directly coupled and hydrogen carrier gaspassed through them in series. In the operation of the unit, a smallamount of charge, i.e., Z-methylpentane, was injected over a period ofabout seconds. The injected material passed to the reactor and then tothe chromatograph columnconductivity cell analyzer.

For each test the reactor was loaded with two milliliters, of catalysthaving a mesh size of 40-60 (ASTM designation E1 1-39) For each test thecharge stock was Z-methylpentane. The hydrogen carrier for the chargewas added at the rate of 40 milliliters per minute, and thetotalchargevolume for each test was 0.01 milliliter. The chromatographcolumn had a diameter of inch and a length of 12 feet, and was operatedat room temperature. The packing consisted of isoquinoline on firebrick.

The neohexane yield and cracked-product yield obtained when employingeach catalyst was determined by measuring the chromatograph peak heights(in arbitrary units). The results are as follows:

It is readily apparent from the above table that maximum neohexane yieldand minimum cracked-product yield were obtained only when the catalystwas prepared in accordance with the method of the present invention.

Example II Yield as Treating Level Measured by Temp, Wt. PercentChromatograph F., at

Peak Heights Max.

Neoherane I Yield Fluorine Sulfur Cs Neohexane It is apparent from theabove tabulation that in all cases a highly active isomerizationcatalyst resulted. Optimum treating levels, as. measured by minimum Cyield and maximum neohexane. yield were a fluorine content of 1.5percent by weight and a sulfur-exposure level of 0.9 percent by weight.

Example III A series of twelve runs were made employing a hexane blendas the charge stock, instead of substantially pure Z-methylpentane as inExamples I and II above. The hexane blend consisted of a non-equilibriumblend of 2-methylpentane, 3-methylpentane, normal hexane, neohexane, anddiisopropyl. The runs were made at varying temperatures with the. hexaneblend being charged either batch-wise or continuously. For the batchexperiments the same apparatus as in Examples I and II was employed.When the hexane blend was charged continuously, the apparatus wasmodified so that the hydrogen stream was first charged to a saturatorwherein it picked up the hexane charge continuously.

The catalyst was prepared in accordance with the method of the presentinvention as. described in Example I, except that quantities ofimpregnating and treating materials were adjusted so that the finishedcatalyst had a platinum content ofv about percent, a chloride content inexcess of 2 percent, a. fluoridecontentof about 2.5 percent, and aresidual sulfur content corresponding to a sulfur-treat level of about1.5 percent. The results are as follows:

Approximate Equilibrium Yield Temperature F. Number of Runs BatchContinuous Neohexane Diisopropyl Charge Charge As shown in the abovetabulation, in all cases equilibrium yields of neohexane and diisopropylwere obtained. When the catalyst accumulates coke, it is readilyregenerated by contact with flue gas containing about 2 percent oxygenat 700 to 1000 F.

It is readily apparent from the above description that the presentinvention provides a catalyst which is substantially non-corrosive, hasa very high isomerization activity, can be readily regenerated, and isinexpensive to produce, particularly since it permits conversion of areforming catalyst to an isomerization catalyst.

Having thus described the invention, what is claimed is:

1. A method for preparing a superior catalyst for isomerization of lighthydrocarbons which comprises impregnating solid hydrous aluminacontaining between about 1 to 30 percent by Weight of combined water inthe presence of between about 0.001 to 0.02 mole of aluminum chlorideper mole of dry A1 with a solution of a platinum compound wherebyplatinum is added thereto in a proportion between about 0.01 and 2.0percent by weight, based on dry A1 0 drying and calcining, impregnatingthe resulting composite with hydrogen fluoride to a fluoride level inthe range of about 0.5 to 5 percent by weight, based on dry A1 0exposing the composite to a substance selected from the group consistingof sulfur, sulfur-containing compounds, and mixtures thereof insufiicient quantity so that the catalyst is contacted with at leastabout 0.1 percent by weight of sulfur, based on dry A1 0 and calcining.

2. The method of claim 1 wherein said platinum compound ischloroplatinic acid.

' 3. The method of claim 1 including the additional step of drying andcalcining the composite after the impregnating step and before theexposing step.

4. In the method of preparing a catalytic composite which comprisesimpregnating solid hydrous alumina containing between about 1 to 30percent by weight of combined water in the presence of between about0.001 to 0.02 mole of aluminum chloride per mole of dry A1 0 with asolution of a platinum compound whereby platinum is added thereto in aproportion between about 0.01 to 2.0 percent by weight, based on dry A10 and drying and calcining, the improvement which comprises impregnatingthe resulting composite with an aqueous solution of hydrogen fluoride toa fluoride level in the range of about 0.5 to 5 percent by weight, againdrying and calcin ing, thereafter contacting the catalyst with anaqueous solution of a sulfur-containing compound in sufficient quantityso that the catalyst is contacted with about 0.1 to 5.0 percent byweight, based on dry A1 0 of sulfur, and again drying and calcining.

5. The method of claim 4 wherein said platinum compound ischloroplatinic acid and said sulfur-containing compound is ammoniumsulfide.

6. The method of claim 4 wherein said platinum compound ischloroplatinic acid and said sulfur-containing compound is hydrogensulfide.

7. A method of preparing a catalytic composite which method comprisesimpregnating calcined alumina containing between about 1 to about 10percent by weight of combined water with an aqueous solution ofchloroplatinic acid and aluminum chloride, drying and calcining theimpregnated alumina, said solution being used in suflicient quantitywhereby after said impregnating, drying and calcining the resultingcomposite contains about 0.6 weight percent platinum and about 1.1weight percent chlorine, based on dry A1 0 treating said composite withan aqueous solution of hydrogen fluoride whereby fluoride is added tosaid composite in an amount of about 1.5 weight percent, based on dry A10 drying and calcining the resulting fluoride-containing composite,treating said fluoride-containing composite with an aqueous solution ofammonium sulfide containing about 0.9 percent by weight of sulfur, basedon dry A1 0 and drying and calcining.

8. A platinum-on-alumina catalyst of improved isomerization activityprepared by impregnating solid hydrous alumina containing between about1 to 30 percent by weight of combined water in the presence of betweenabout 0.001 to 0.02 mole of aluminum chloride per mole of dry A1 0 witha solution of a platinum compound whereby platinum is added thereto in aproportion between about 0.01 and 2.0 percent by weight, based on dry A10 drying and calcining, impregnating the resulting composite withhydrogen fluoride to a fluoride level in the range of about 0.5 to 5percent by weight, based on dry A1 0 exposing the composite to asubstance sel cted from the group consisting of sulfur,sulfur-containing compounds, and mixtures thereof, in suflicientquantity whereby said composite is contacted with at least about 0.1percent by weight of sulfur, based on dry A1 0 and calcining.

References Cited in the file of this patent UNITED STATES PATENTS2,659,701 Heard et a1 Nov. 17, 1953 2,840,514 Brennan June 24, 19582,840,528 Mills June 24, 1958 2,841,626 Holzman et a1. July 1, 19582,863,825 Engel Dec. 9, 1958 2,891,965 Voltz June 23, 1959 2,905,736Belden Sept. 22, 1959

1. A METHOD FOR PREPARING A SUPERIOR CATALYST FOR ISOMERIZATION OF LIGHTHYDROCARBONS WHICH COMPRISES IMPREGNATING SOLID HYDROUS ALUMINACONTAINING BETWEEN ABOUT 1 TO 30 PERCENT BY WEIGHT OF COMBINED WATER INTHE PRESENCE OF BETWEEN ABOUT 0.001 TO 0.02 MOLE OF ALUMINUM CHLORIDEPER MOLE OF DRY AL2O3 WITH A SOLUTION OF A PLATINUM COMPOUND WHEREBYPLATINUM IS ADDED THERETO IN A PROPORTION BETWEEN ABOUT 0.01 AND 2.0PERCENT BY WEIGHT, BASED ON DRY AL2O3, DRYING AND CALCINING,IMPREGNATING THE RESULTING COMPOSITE WITH HYDROGEN FLUORIDE TO AFLUORIDE LEVEL IN THE RANGE OF ABOUT 0.5 TO 5 PERCENT BY WEIGHT, BASEDON DRY AL2O3, EXPOSING THE COMPOSITE TO A SUBSTANCE SELECTED FROM THEGROUP CONSISTING OF SULFUR, SULFUR-CONTAINING COMPOUNDS, AND MIXTURESTHEREOF IN SUFFICIENT QUANTITY SO THAT THE CATALYST IS CONTACTED WITH ATLEAST ABOUT 0.1 PERCENT BY WEIGHT OF SULFUR, BASED ON DRY AL2O3, ANDCALCINING.